Hardware backdoors in some x86 CPUs
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A hardware backdoor in VIA C3 x86 CPUs allows userland code to access kernel data.
Project Rosenbridge reveals a hardware backdoor in some desktop, laptop, and embedded x86 processors, specifically VIA C3 CPUs. The backdoor is a non-x86 core that, when enabled, lets ring 3 code bypass protections to read and write ring 0 data. It is enabled by default on some systems. Researchers provide tools to check and close the backdoor. The vulnerability is limited to the C3 series; later CPUs lack the feature. The work is presented as a case study on how backdoors may arise in complex processors.
What commenters are saying
Commenters highlight that this backdoor only affects decades-old VIA C3 processors, introduced in 2001, and that the alternate instruction set is documented in datasheets. Some argue calling it a backdoor is misleading since it was likely a debugging feature. Others note that documenting a backdoor doesn't negate its danger, especially when enabled by default on ATMs and medical hardware. The broader point is that hidden coprocessors in modern hardware pose a significant supply chain risk, though state-level targeting is unlikely for typical users.